Mechanism to Raise the Efficiency of a Reciprocating Refrigeration Compressor

ABSTRACT

An improvement to raise the efficiency of a reciprocating refrigeration compressor, the improvement comprising a channel in the piston that transfers pressure from the clearance volume of the cylinder to the low pressure side of the piston when an opening of the channel aligns with a groove or a duct in the cylinder wall. Alternately, the channel comprises a ball extending from and held to the clearance volume opening of the channel by a spring. When the spring is compressed, the ball is moved from the opening, and pressure in the clearance volume is transferred to the low pressure side of the piston.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of and claims priority to Chinese Patent Application No. 2010101014022 filed Jan. 27, 2010, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to reciprocating refrigeration compressors and specifically to improving efficiency by improving the structure of the valve plate, piston, and cylinder bore.

BACKGROUND OF THE INVENTION

A reciprocating refrigeration compressor is composed of main parts, including the body, crankshaft, cylinder cover, valve plate, piston, connecting rod, motor, motor cover, bearing housing, bottom plate, and the like. Typically, an electric motor drives the crankshaft, which is connected to a connecting rod and piston. The crankshaft moves the piston upward and downward. A valve plate on the cylinder plane has a suction port and a discharge port. As the piston moves downward on the suction stroke, pressure is reduced in the cylinder. Refrigeration systems use a circulating liquid refrigerant that enters the compressor as a vapor. When the pressure falls below that in the compressor suction line, the pressure differential causes the suction valves to open and forces the refrigerant vapor to flow into the cylinder.

As the piston reaches the bottom of its stroke and starts upward on the compression stroke, pressure is developed in the cylinder, forcing the suction valves closed. The pressure in the cylinder continues to rise as the piston moves upward, compressing the vapor trapped in the cylinder. When the pressure in the cylinder exceeds the pressure existing in the compressor discharge line, the discharge valve is forced open, and the compressed gas flows into the discharge line which is connected to the condenser.

When the piston starts downward, the reduction in pressure allows the discharge valve to close because of the higher pressure in the condenser and discharge line, and the cycle is repeated.

Three main factors affect compressor efficiency: 1) The seating of the valves; 2) the temperature of the cylinder walls (if the cylinder wall are hot and suction gas entering the cylinder on the intake stroke is heated by the cylinder walls, the gas expands, resulting in a reduced weight of gas entering the compressor); and 3) the clearance volume of the cylinder.

The most important factor affecting compressor efficiency is clearance volume. The clearance volume is composed of following five areas: 1) clearance above the piston; 2) clearance for reed thickness; 3) discharge ports on valve plate; 4) clearance between the piston and the cylinder wall; and 5) clearance for the reed opening and stopping.

When the piston starts down on the suction stroke, the residual high pressure gas in the clearance volume expands and its pressure is reduced. No vapor from the suction line can enter the cylinder until the pressure in the cylinder has been reduced below the suction line pressure. Thus, the first part of the suction stroke is actually lost from a capacity standpoint, and as the compression ratio increases, a greater percentage of the suction stroke is occupied by the residual gas.

A problem exists in the efficiency of the compressor. Compressor efficiency is typically effected by the clearance volume, rate of heat transfer, valve and piston leakage, vapor load and the like. For example, in a typical three-cylinder compressor having pistons with a diameter of 65 mm, a high temperature results in a compression ratio from 4-8; a media temperature application in a compression ratio from 7-12, and low temperature application results in a compression ratio from 8-18. Because of the difference between discharge pressure vs. suction pressure, the efficiency effects are 12-19%, 16-28%, 19-41%, respectively. The larger the compression ratio, the more serious the efficiency effect will be.

Regular improvements from many compressor builders are: 1) Mill the reed shape to certain depth (usually is same as reed thickness) on the top of piston; 2) Reduce the thickness of valve plate; and 3) Use a model called discs compressor, which has different valve plate designing to eliminate discharge port clearance volume. All these methods will reduce the clearance volume, thus raising the compressor efficiency to certain level, but the clearance volume issues with high temperature and high pressure still exists. A further difficulty with existing methods is that they require major changes to the design of the compressor. There is a long-standing need for an improvement to compressor efficiency that is simple and does not require major design changes.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is a device and method of improving the efficiency of a reciprocating refrigeration compressor comprising a cylinder body and a piston. The method comprises creating at least one channel in the piston, such that, when a compression stroke is completed the channel transfers a pressure in a clearance volume to a low pressure side of the piston.

In an embodiment, at least one groove is created in a wall of the cylinder body. In addition, each channel has a first end comprising an opening on the exterior diameter of the piston between a pressure ring and an oil ring and a second opening on the low pressure side of the piston. When a compression stroke is completed, each opening of the channel on the exterior diameter of the piston aligns with each groove to transfer a pressure in the clearance volume to the low pressure side of the piston.

In an embodiment, a duct is created in the cylinder body. The duct extends from an opening at the clearance volume side of the cylinder body to a second opening in the wall of the cylinder. When a compression stroke is completed, each channel aligns with each duct and pressure in the clearance volume is transferred to the low pressure side of the piston through the ducts and the channels.

In an embodiment, each channel comprises a first end comprising a first opening on the clearance volume side of the piston and a second opening on the low pressure side of the piston. The first end opening has a diameter smaller than a second diameter of the remainder of the channel. Each first end comprises a ball, a spring, and a set screw. The ball has a diameter greater that the first end diameter and less than the second diameter. The ball is held against the opening, which is spherical shaped, by the spring, to seal the first end opening. A portion of the ball extends from the top of the piston into the clearance volume. When the piston moves up and down normally, high pressure does not cause compression of the spring, so that the opening remains sealed by the ball. When the piston completes a compression stroke, the portion of the ball extending from the opening contacts the valve plate. The upward movement of the piston pushes the ball into the valve plate. Contact with the valve plate compresses the spring and moves the ball down into the first end opening, thus opening the channel. High pressure in the clearance volume flows through the channel to the low pressure side of the piston. As the piston continues its cycle and moves downward from the valve plate, the ball is resealed in the opening by energy released from the spring.

The present invention is an improvement for a reciprocating refrigeration compressor, comprising a cylinder body and a piston. The improvement comprises at least one channel in the piston connecting the clearance volume to a low pressure side of the piston.

In an embodiment, the improvement comprises at least one groove in a wall of the cylinder body. In addition, each channel comprises a first end having an opening on a exterior diameter of the piston between the pressure ring and the oil ring and a second opening on the low pressure side of the piston. When a compression stroke is completed, each channel aligns with each groove to transfer pressure in the clearance volume to the low pressure side of the piston.

In an embodiment, the improvement comprises at least one duct in the cylinder body. The duct has an opening extending from the clearance volume to a second opening at a point in a wall of the cylinder. In addition, each channel comprises a first end having an opening on a exterior diameter of the piston between the pressure ring and an oil ring. When a compression stroke is completed, each channel aligns with each duct and pressure in the clearance volume is transferred to the low pressure side of the piston through the ducts and the channels.

In an embodiment, the improvement comprises a channel comprising a first end having a first opening on the clearance volume side of the piston and a second opening on the low pressure side of the piston. The first end opening has a diameter smaller than a second diameter of the remainder of the channel. Each first end comprises a ball, a spring, and a set screw. The ball extends from the first end opening and has a diameter greater that the first end diameter, but less than the second diameter. The ball is held against the opening by the spring with a portion of the ball extending from the top of the piston into the clearance volume to seal the first end opening of the channel. The ball and spring work together to open the channel when the ball is pressed and the spring is compressed, and to close the channel when the spring is extended.

The present invention addressed the issue of high pressure in clearance volume affecting the efficiency of a refrigeration compressor with a new technical method that releases the high pressure simply and in very short time. The present invention provides a substantial improvement in the volumetric efficiency of the compressor by releasing the high pressure from clearance volume of the compressor. Among the advantages of this invention are:

1) Without the high pressure in the clearance volume, the efficiency effect from that will be controlled to about 2% only, thus, the compressor efficiency will be raised dramatically.

2) Without the high pressure, high temperature will be reduced automatically. Without high temperature, the density of vapor will not have extra expansion. Thus, the extra compressor efficiency will be raised.

3) The high pressure will be released to compressor crankcase, which will raise internal pressure. Thus the suction pressure will be raised, and this result will be really helpful to compressor system capacity.

4) High pressure is the main reason for noise. Without high pressure, the compressor will be quieter.

5) Reducing the possibility of “slugging.” Slugging occurs when the compressor vapor condenses to a liquid upon entering the compressor. Because liquid does not compress, slugging leads to failure of the compressor.

As used herein, “approximately” means within plus or minus 25% of the term it qualifies. The term “about” means between ½ and 2 times the term it qualifies. The term “substantially” means that ninety-five percent of the values of the physical property when measured along an axis of, or within a plane of or within a volume of the structure, as the case may be, will be within plus or minus 10% of a mean value.

As used herein, “implementation” is interchangeable with “embodiment.”

As used herein, “top” and “up” mean furthest away from the crankcase, while “bottom” and “down” mean closest to the crankcase.

Numerical ranges as used herein are intended to include every number and subset of numbers contained within that range, whether specifically disclosed or not. Further, these numerical ranges should be construed as providing support for a claim directed to any number or subset of numbers in that range.

The methods of the present invention can comprise, consist of, or consist essentially of the essential elements and limitations of the invention described herein, as well as any additional or optional components, or limitations described herein or otherwise useful in compositions and methods of the general type as described herein.

All references to singular characteristics or limitations of the present invention shall include the corresponding plural characteristic or limitation, and vice versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made. Definitions used herein are intended to supplement and illustrate, not preclude, the definitions known to those of skill in the art.

All combinations of method or process steps as used herein can be performed in any order, unless otherwise specified or clearly implied to the contrary by the context in which the referenced combination is made.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is for the implementation 1, the A-A cross-sectional view of reciprocating motor-compressor when almost finishing the compression stroke.

FIG. 2 is for the implementation 1, the top view without valve plate mounting.

FIG. 3 is for the implementation 1, the B-B sectional view and also shows the piston moving upward and downward.

FIG. 4 is for the implementation 1, partial enlarged drawing for C area.

FIG. 5 is for the implementation 2, the sectional view of B-B.

FIG. 6 is for the implementation 2, partial enlarged drawing for D.

FIG. 7 is for the implementation 3, whole cross-sectional view of piston moving.

FIG. 8 is for the implementation 3, partial enlarged drawing for A.

FIG. 9 is for the implementation 3, the whole cross section of drawing for piston almost completed compression stroke.

FIG. 10 is for implementation 3, the partial enlarged drawing for B.

FIG. 11 is for implementation 3, the partial enlarged drawing for E.

DETAILED DESCRIPTION OF THE INVENTION

The invention is a mechanism of raising the efficiency of the refrigeration compressor. This mechanism includes cylinder body, a piston attached to a crankcase, suction valve, discharge valve, and valve plate, as well as modifications to existing compressors. The specialty for this mechanism is that there is a channel to connect the high pressure side of the clearance volume above the piston to the low pressure side below the piston through channels within the piston only or on the piston and cylinder body together. The invention substantially releases the high pressure in the clearance volume at the end of compression stroke. Reduction of pressure in the clearance volume increases the efficiency of the compressor as long as other factors effecting efficiency remain constant.

The invention has several methods of connecting the high pressure side and low pressure side with channel. First, a channel is bored between the clearance volume (high pressure) and crank case (low pressure). The channel is formed by preferably by drilling one small hole with size range of about 3-5 mm on each reed stopping deck along the cylinder wall to the depth of about 0.1 to about 0.3 mm under upper piston ring. This depth is very critical. Too deep will cause the high pressure releasing too earlier, which will cause efficiency lost. Too shallow will cause the high pressure not be able to release in short time. Also, several holes are drilled through the piston outside diameter between the piston rings. When the piston completes the compression stroke, a through channel is formed between the clearance volume and the crank case from an opening on the cylinder bore deck that is interconnected to openings on the outer diameter of the sides of the piston between the piston rings. Because of the pressure balance, when the channel is opened, the high pressure in the clearance volume is released suddenly, and the new pressure will be equal to suction pressure.

In an alternate embodiment, a channel is formed by drilling a hole on the center of piston from the crankcase side with two diameters: a smaller size for the opening and a bigger size for remainder of the channel. A metal ball, spring, and set screw are mounted at the opening. The diameter of opening on the piston is smaller than the diameter of the metal ball, but the internal diameter of the channel on the piston is bigger than the diameter of metal ball. The transition between the sizes of the holes is sphere-shaped to allow the ball to sit and seal.

When finishing assembling the ball, the spring, and a set screw, through adjusting the set screw, it will push the spring to apply a force to the ball, so that the ball is forced to sit on the surface of sphere shape, and seal this through hole. The partial ball extends from the top of the piston. When piston moves up and down normally, the high pressure is not leaked from this hole and the contact area between the ball and piston. When the piston completes the compression stroke, the ball on the piston touches the valve plate, and is squeezed down, thus the open channel is formed. The clearance volume with high pressure above the piston is connected with low pressure side. In this way, the high pressure is released from the clearance volume.

The improvement is shown by the following examples relating to the Figures:

In an embodiment depicted in FIGS. 1-4, the invention provides a mechanism of raising the efficiency of the reciprocating refrigeration compressor. As shown in FIG. 1, the mechanism includes cylinder body 1, piston 2, suction reed 3 (see FIG. 3), discharge reed 4, and valve plate 5. Two grooves 6 are milled along the cylinder bore 7, located on each stopping deck 13 (see FIG. 2). The grooves' 6 length is such that it allows high pressure in the clearance volume 12 (see FIG. 4) to be released, and allow the piston 2 to finish its compression stroke without losing high pressure early which reduces the efficiency. Several holes 8 are drilled through the piston 2 outside diameter between pressure ring 9 and oil ring 10. The holes 8 connect the outside diameter 2 a of the piston 2 to the low pressure side of the piston inside the cylinder toward the crankcase 18. When the piston 2 completes the compression stroke, a through channel 11 will be formed automatically from the clearance volume 12 to the grooves 6 on the cylinder bore stopping deck 13, then going through to the area between two piston rings 9&10, finally through the holes 8 on the piston 2 outside diameter 2 a, flowing into the crankcase side of the piston 18.

In an embodiment depicted in FIGS. 5 and 6, the groove 6 on the cylinder bore deck 13 described above is replaced with an “L” shaped duct 14. Ducts 14 are drilled on the cylinder stopping deck 13 parallel to the piston 2, and a second part of the duct 14 a perpendicular to the piston 2. The parts of the duct 14, 14 a are interconnected to form a shape substantially similar to a letter “L”. The second part of the duct 14 a is situated to align with the opening 15 of the channel 11 in the piston 2. The embodiment performs in a similar fashion as described above.

In an embodiment depicted in FIGS. 7-11, a channel is formed (preferably by drilling) on the center of the piston from the crankcase side. The channel has two diameters: a smaller size for at a first end 20, and a slightly bigger size for the remainder of the channel 21. One metal ball 22, one spring 23, and one set screw 24 is mounted within the channel 21 of the piston 2 at the first end 20. The diameter of the first end 20 on the top of the piston 2 must be smaller than the diameter of the metal ball 22, but internal diameter of hole 21 on the piston 2 must be bigger than the diameter of metal ball 22. The transition with two sizes first end 20 and hole 21 will be sphere shape to allow the ball 22 to sit and seal the first end 20.

As shown in FIGS. 9-11, when finishing assembling the ball 22, the spring 23, and a set screw 24, through adjusting the set screw 24, it will push the spring to apply a force to the ball 22, so that the ball 22 will be forced to sit on the surface of sphere shape, and seal first end 20. The partial ball 22 will be out of the top of the piston 2. When piston 2 moves up and down normally, the high pressure would not be leaked from first end 20 and the contact area between the ball 22 and piston 2. When the piston 2 completes the compression stroke, the ball 22 on the piston 2 will touch the valve plate 5, and will be squeezed down, thus the open channel will be formed automatically. The clearance volume with high pressure above the piston 2 will be connected with low pressure side. In this way, the high pressure will be released then.

Accordingly, this invention is intended to embrace all alternatives, modifications, and variations that fall within the spirit and broad scope of the claims. 

1. A method of improving the efficiency of a reciprocating refrigeration compressor comprising a cylinder body and a piston, the method comprising creating at least one channel in the piston, such that, when a compression stroke is completed, the channel transfers a pressure in a clearance volume to a low pressure side of the piston.
 2. The method of claim 1 further comprising creating at least one groove in a wall of the cylinder body, and wherein each channel comprises a first end comprising an opening on a exterior diameter of the piston between a pressure ring and an oil ring and a second opening on the low pressure side of the piston such that, when a compression stroke is completed, the channel opening on each exterior diameter of the piston aligns with each groove to transfer a pressure in the clearance volume to the low pressure side of the piston.
 3. The method of claim 1 further comprising creating at least one duct in the cylinder body, the duct comprising an opening extending from the clearance volume to a second opening at a point in a wall of the cylinder such that, when a compression stroke is completed, each channel aligns with each duct and a pressure in the clearance volume is transferred to the low pressure side of the piston through the ducts and the channels.
 4. The method of claim 1 wherein: the channel comprises a first end comprising a first opening on the clearance volume side of the piston and a second opening on the low pressure side of the piston, the first end opening having a diameter smaller than a second diameter of the remainder of the channel, each first end comprising a ball, a spring, and a set screw, said ball extending into the opening and having a diameter greater that the first end diameter and less than the second diameter, the ball held against the opening by the spring such that a portion of the ball extends from the top of the piston into the clearance volume to seal the first end opening, and wherein, when the piston completes a compression stroke, the portion of the ball extending from the opening contacts the valve plate, compressing the spring to move the ball from the opening to allow high pressure in the clearance volume to flow through the channel to the low pressure side of the piston.
 5. An improved reciprocating refrigeration compressor comprising a cylinder body and a piston, the improvement comprising at least one channel in the piston, each channel connecting a clearance volume at a first side of the piston to a low pressure side of the piston.
 6. The improved compressor of claim 5 further comprising at least one groove in a wall of the cylinder body and wherein each channel comprises a first end comprising an opening on a exterior diameter of the piston between a pressure ring and an oil ring and a second opening on the low pressure side of the piston such that, when a compression stroke is completed, each channel aligns with each groove to transfer a pressure in the clearance volume to the low pressure side of the piston.
 7. The improved compressor of claim 5 further comprising at least one duct in the cylinder body, the duct comprising an opening extending from the clearance volume to a second opening at a point in a wall of the cylinder, and wherein each channel comprises a first end comprising an opening on a exterior diameter of the piston between a pressure ring and an oil ring, such that, when a compression stroke is completed, each channel aligns with each duct and a pressure in the clearance volume is transferred to the low pressure side of the piston through the ducts and the channels.
 8. The improved compressor of claim 5 wherein the channel comprises a first end comprising a first opening on the clearance volume side of the piston and a second opening on the low pressure side of the piston, the first end opening having a diameter smaller than a second diameter of the remainder of the channel, each first end comprising a ball, a spring, and a set screw, said ball extending into the first end opening and having a diameter greater that the first end diameter and less than the second diameter, such that the ball seals the channel when the spring is extended and the channel is open when the spring is compressed. 